DESCRIPTION: (Applicant's Abstract)Organ formation requires many steps to assemble cells from different origins with specific fates to form a functional unit. How to make a properly formed organ and maintain its normal function is a vital task for complex organisms. Abnormalities in genes that are involved in the patterning and/or function of organs often cause embryonic lethality, or induce severe health problems later in life, as evident in congenital heart failure, arrhythmia, leukemia and diabetes. Understanding how the organs are patterned, which genes are involved in organ patterning and/or function, and how these genes interact with each other are important issues for studying vertebrate organ formation and function. In-depth knowledge of these issues not only will facilitate further studies on the basic mechanisms of organogenesis, but also will lead to the development of early diagnosis and treatment for human diseases. To understand how vertebrate organs are formed and to identify genes and pathways that are involved in vertebrate organogenesis. We will take a combination of genetic, embryological and genomic approach using zebrafish as a model system. Zebrafish is the vertebrate model organism that can facilitate large-scale phenotype-based genetic screen. Recent advances in zebrafish genomic resources allow rapid mapping and positional cloning of the mutated genes. Furthermore, the zebrafish organ systems are the simplest forms of all vertebrates. The transparent nature of the zebrafish embryos makes it suitable for the application of the GFP technology. We will generate a transgenic line in which six organ primordia are marked by GFP expression. We will use these fish to construct a 4-dimensional fate map for these organs. This information will provide foundation for future studies of vertebrate organ formation. We will mutagenize these fish with ENU and screen for mutations affecting zebrafish organ formation and function. We will also develop reagents and technologies to facilitate a retroviral insertional gain-of-function screen. Mutations identified from this screen will provide entry points to dissect genetic and molecular pathways involved in vertebrate organogenesis.